JPH0352056B2 - - Google Patents

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an electrophotographic photoreceptor.

(Prior Art) In recent years, charge-generating materials have come to be widely used not only in electrophotographic copying machines but also as photosensitive materials in laser printers, LED printers, image sensors, and the like. As one of these charge-generating materials, it has been proposed to use perylene-based dyes as a charge-generating substance that is sensitive to light with a wavelength of 400 to 600 nm.

(Problems to be Solved by the Invention) Perylene dyes that have been proposed so far have low sensitivity due to exposure after charging, especially when used as photosensitive materials for electrophotography, and when the normal Carlson process is repeated sequentially. The charging potential decreases,
In addition, the residual potential after exposure gradually increased, resulting in low image density in the image area and a lot of fog on the white background, making it impossible to obtain high-quality images, so it was not put into practical use. .

(Means for Solving the Problems) As a result of intensive research to solve the problems of the above-mentioned conventional technology, the present inventor found that the photoconductivity of perylene dyes depends on the manufacturing conditions of the perylene dyes. When the perylene dye is adjusted to have a particle size within a specific range, the above-mentioned problems of the prior art can be solved and an electrophotographic photoreceptor with high performance that can be put to practical use can be obtained. The present invention was completed based on the knowledge that

That is, the present invention provides an electrophotographic photoreceptor comprising a photosensitive layer containing a charge generating material in a binder resin, wherein the charge generating material is represented by the following formula and has an average particle diameter of 0.05 to 0.1 μm. This is an electrophotographic photoreceptor characterized by the following.

(Preferred Embodiment) To explain the present invention in detail, the perylene pigment used in the present invention has the above structural formula, and is a substance conventionally known as a high-grade organic pigment with excellent properties. It can be easily synthesized by conventionally known methods and is also easily available on the market. These known perylene pigments generally have a particle size of less than 0.05 μm, and have high performance as organic pigments at these particle sizes. However, when organic pigments with these known particle sizes are mixed with a binder resin to create a photoreceptor for electrophotography, the dispersibility is very poor, and even if the dispersibility is sufficient, it is difficult to use for electrophotography. It did not exhibit sufficient performance as a photoreceptor.

As a result of various studies on the relationship between the particle diameter of these perylene dyes and their use as photosensitive materials, the present inventor determined that the average particle diameter of the perylene dyes should be 0.05 to 0.1 μm, preferably so that most of the particles fall within the above range. It was discovered that when the particle size is controlled, the dispersibility of the perylene dye in the binder resin becomes better, and the performance of the resulting photoreceptor for electrophotography is greatly improved. .

The perylene dyes used in the present invention are conventional perylene dyes such as xylene, O-dichlorobenzene, nitrobenzene, dimethylamide, dimethylformamide, N-methyl-2-pyrrolidone, methyl ethyl ketone, cyclohexanone, pyridine, quinoline, etc. By treating with an organic solvent, the particle size can be adjusted to a range of 0.05 to 0.1 μm.

A particularly preferred treatment method is to dissolve freshly produced perylene dyes or commercially available perylene pigments in a strong solvent such as concentrated sulfuric acid, and then precipitate the resulting crystals in a non-solvent such as water. Once made into an amorphous form, the perylene-based The average particle size of the dye
It can be in the range of 0.05 to 0.1 μm.

(Function/Effect) When the perylene dye used in the present invention as described above is dispersed in a binder resin to form a photoreceptor for electrophotography, it is compared with a photoreceptor for electrophotography using a conventional perylene dye. As a result, it is possible to obtain an electrophotographic photoreceptor that has extremely excellent sensitivity, has excellent repeatability in the Carlson process, and shows no deterioration in its electrophotographic properties even after repeated use many times. be.

(Example) Next, the present invention will be specifically explained by giving reference examples, examples, comparative examples, and measurement examples. In the text, parts or percentages are based on weight unless otherwise specified.

Reference example 1 Formula made amorphous by sulfuric acid method 250 parts of crude in 1500 parts of nitrobenzene and milled in a magnetic ball mill at room temperature for 48 hours. After grinding, add 1,500 parts of methanol and separate by filtration.
Wash thoroughly with methanol. dry and crush
225 parts of perylene dye having an average particle diameter of 0.075 μm were obtained.

Reference Example 2 250 parts of PV Fast Red B (manufactured by Hoechst) are dispersed in 5000 parts of dimethylformamide and stirred at room temperature for 15 hours. It is then filtered and washed with methanol. After drying and crushing, the average particle size of 240 parts is 0.06 μm.
A perylene dye was obtained.

Furthermore, for reference, electron micrographs of the product of the present invention (Reference Example 1) (FIG. 1) and a commercially available pigment having the same structural formula as the product (FIG. 2) are shown.

In addition, PV Fast Red B is CI Pigment
Red149 is represented by the structural formula below.

Example 1 A photosensitive solution was prepared according to the following formulation.

Polyvinylcarbazole (Tubicol 210)
100 parts perylene dye of Reference Example 1 (average particle size 0.075μ
m) 5 parts Polyester resin (Vylon 200) 10 parts 2,5-dichloro-p-benzoquinone 5 parts Mixed solvent (toluene/THF=8/2) 1500 parts The above mixture was placed in an alumina ball mill, and
After time dispersion, the coating was applied to a 100 μm aluminum plate using a wire bar, and the coating and drying was carried out so that the film thickness after drying was 15 μm to obtain a photoreceptor 1.

Example 2 Photoreceptor 2 was obtained in the same manner as in Example 1 using the perylene dye of Reference Example 2 having an average particle diameter of 0.06 μm.

Comparative example 1 Commercially available PV Fast Red B (average particle size 0.03 μm,
A photoreceptor 3 was obtained in the same manner as in Example 1 using the untreated photoreceptor (manufactured by Hoechst).

Comparative Example 2 250 parts of PV Fast Red B (manufactured by Hoechst) is dispersed in 2500 parts of nitrobenzene and stirred at 95°C for 10 hours. It is then filtered and washed with methanol. After drying and pulverizing, 240 parts of perylene pigment having an average particle diameter of 0.2 μm were obtained. Photoreceptor 4 was obtained in the same manner as in Example 1 using this dye.

Measurement Example 1 Electrostatic paper analyzer SP428 manufactured by Kawaguchi Electric Manufacturing Co., Ltd. was used to evaluate electrophotographic special products.

Measurement conditions Measurement mode Statute No. 1 Applied voltage +6.0KV Exposure intensity (surface illuminance) 25Lux (Tungsten lamp 2856℃K) Result Initial charging potential (V ₀ volts) Photoconductor 1 Photoconductor 2 Photoconductor 3 Photoconductor 4 +630 +615 +580 +620 Potential retention rate after 10 seconds in the dark (%) Photoconductor 1 Photoconductor 2 Photoconductor 3 Photoconductor 4 92 90 85 95 Half-attenuation exposure (E1/2Lux・sec) Photoconductor 1 Photoconductor 2 Photoconductor 3 Photoconductor 4 5.5 6.0 9.5 9.8 From the above results, it can be seen that the present invention is superior in both dark decay characteristics and sensitivity.

Measurement Example 2 The characteristics of photoreceptors 1, 2, and 3 were measured over 1000 cycles, and the results shown in FIG. 3 were obtained.

Although the charging potential of photoreceptor 3 has changed significantly, the charging potentials of photoreceptors 1 and 2 are good and hardly change from the initial ones, indicating the remarkable effect of the present invention.

[Brief explanation of drawings]

In the accompanying drawings, Figure 1 is an electron micrograph (magnification: 30,000) of the crystal structure of the perylene pigment used in the present invention (Reference Example 1), and Figure 2 is an image of a commercially available pigment having the same structure as the product. An electron micrograph (30,000 magnification) of the structure of the crystal is shown. FIG. 3 shows the measurement results of the repeatability of the photoreceptor of the present invention and the photoreceptor of the comparative example.

Claims (1)

[Scope of Claims] 1. An electrophotographic photoreceptor comprising a photosensitive layer containing a charge-generating material in a binder resin, wherein the charge-generating material is represented by the following formula and has an average particle diameter of 0.05 to 0.1 μm. An electrophotographic photoreceptor characterized by: